Microstructure and mechanical property of a new IPS-Empress 2 dental glass-ceramic / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the microstructure and mechanical properties of a new IPS-Empress 2 dental glass-ceramic.</p><p><b>METHODS</b>AFM, SEM and XRD were used to analyze the microstructure and crystal phase of IPS-Empress 2 glass-ceramic. The flexural strength and fracture toughness were tested using 3-point bending method and indentation method respectively.</p><p><b>RESULTS</b>IPS-Empress 2 glass-ceramic mainly consisted of lithium disilicate crystal, lithium phosphate and glass matrix, which formed a continuous interlocking structure. The crystal phases were not changed before and after hot-pressed treatment. AFM showed nucleating agent particles of different sizes distributed on the highly polished ceramic surface. The strength and fracture toughness were 300 MPa and 3.1 MPam(1/2).</p><p><b>CONCLUSION</b>The high strength and fracture toughness of IPS-Empress 2 glass ceramic are attributed to the fine lithium disilicate crystalline, interlocking microstructure and crack deflection.</p>

Characterization of N-glycan mapping of bioengineering recombinant erythropoietin by capillary electrophoresis with laser-induced fluorescence / 药学学报

<p><b>AIM</b>N-Glycans in recombinant human erythropoietin (EPO) are essential to in vivo biological activity. This paper is to develop a method for mapping sialyated or asialyated N-glycans of EPO.</p><p><b>METHODS</b>At first, N-glycans linked to asparagines in glycoprotein EPO were released by peptide N-glycosidase F. To map asialyated N-glycans, sialic acid in N-glycans were removed by incubating N-glycans with sialidase. Oligosaccharides were labeled with a sensitive fluorescent dye 8-aminopyrene-1,3,6-trisulfonate (APTS), and all of the labeled oligosaccharides released from EPO were mapped by capillary gel electrophoresis with laser-induced fluorescence. The relationship between N-glycans and bioactivity of EPO was investigated on the basis of N-glycan mapping spectra.</p><p><b>RESULTS</b>N-Glycans of seven different batches of EPO were mapped. Each sample was analysed twice, with and without sialidase treatment. The results showed that N-glycans of each sample were approximately the same. But when the expression vector was different, the types of N-glycans and their relative content were quite different. In case of asialyated N-glycan mapping, the retention time of each oligosaccharide delayed greatly, and most importantly, the resulted sialic acid peak can be used as a quantitative standard to determine sialic acid content in N-glycans of EPO. In addition, the difference of N-glycan mapping was observed when the in vivo biological activity of EPO was different.</p><p><b>CONCLUSION</b>The approach in this article for determining N-glycan mapping can be applied to determine the source of EPO and the difference between each batch. It is also a suitable tool for routinely controlling the inner quality of EPO by coupled with peptide mapping.</p>